This invention relates to nozzles for dispensing gasoline into vehicle fuel tanks and more specifically to an interlock system to prevent dispensing of gasoline until the discharge spout of a nozzle is inserted into the vehicle fuel pipe.
Current environmental regulations will require in some areas that gasoline vapors displaced from a vehicle fuel tank while being filled are to be recovered in order to prevent their escape into the atmosphere. As part of these requirements, it is foreseeable that an interlock system may be required at some time in the future to prevent the dispensing of gasoline until the vapor receiving system is in contact with the vehicle fuel tank. Even if such a requirement never materializes, it is still desirable to have such an interlock system to encourage the filling station operator to have the vapor receiving system properly in place against the fillpipe.
The prior art has shown many designs for providing such an interlock system. One common method is to use a mechanical linkage between the face seal of the vapor receiving system and the automatic shut-off system within the nozzle housing itself. This type of a system tends to become overly complicated and adds to the weight of the nozzle as well as to the cost of construction and maintenance. Other designs include a valve located within the discharge spout and connected to the vent line which leads to the automatic shut-off system in the nozzle housing. This valve is then connected to the vapor receiving system in such a manner that it is closed when the vapor receiving system is not in contact with the vehicle fillpipe, thereby preventing the dispensing of gasoline. While this particular design is capable of working, it has at least one drawback in that the linkage mechanism between the valve and the vapor receiving system can greatly limit the flexibility of the vapor receiving system itself, thereby increasing the possibility of not obtaining a tight seal against the vehicle fillpipe.
Preferably, such an interlock system should be designed in a way that does not interfere with the movement of the vapor receiving system so that a tight seal is formed reliably each time the nozzle is inserted into the fillpipe. Also, its design should be simple to permit ease of operation as well as to minimize manufacturing costs. The interlock system should also be designed so that it operates automatically during normal use of the nozzle, but also permits a manual overriding of the system for filling tanks with unusual fillpipe designs.